Home heating systems which also supply hot water are known in which a heavy cast iron boiler has a coil immersed in a portion thereof which is used to heat domestic hot water. In such systems the hot water is that used by the system for heating the home and, as such, the temperature of the hot water is not regulated by factors other than the temperature needed for heating purposes. In addition, such heating systems utilizing, for example, a large cast iron boiler are expensive and bulky. Furthermore, such heating systems cannot be substantially entirely preplumbed at a factory since much of the piping for the heating system is positioned in the home. Ordinarily such systems are so large that they must be located inside the home, such as in the basement; otherwise, they will radiate large amounts of heat to the outside in cold weather or, alternatively, require bulky and/or expensive insulation.